Production of isophorone and related products



May 7, 1946- s..A. BALLARD TAL 2399,976. PRODUTIORt 0F ISOPHORONE A ND RELATED PRODUCTS l Filed Jan. 2a, 194s Cooler and Separaror Organic Lager co Recovzrg Sqs'l'zm Kdom Pressure l Requlminq Valve Invenior: Szavzr A. Bmlard Vernon E. Haurq Bq `H'wr AHorncL:

Patented May 194e PRODUCTION OF'ISOPHORONE AND RELATED PRODUCTS scrivere. Ballard, oakland, and Vernon n. new. El Cerrito, Calif., assignors to Shell Develop'- ment Company,

San Francisco, Calif., a corporation of Delaware i Application January as, nos, serial No. 474,06@

1o claims. (c1. zoo-5st) This invention relates to a process for the production oi isophorone and related products. More particularly, the invention pertains to a method of manufacture wherein s. saturated ketone of trom Zi to carbon atoms undergoes condensation with cycliation in the presence of a dilute adueous solution of an alkali metal hydroxide to produce an unsaturated alicarbocyclic ketone like isophorone or homo-isophorones.

it is an object of the present invention to provide e. processI applicable in effecting the condensation of saturated ketones containing from 3 to 5 carbon atoms in a continuousmanner.

Another object is to provide a process yfor producing isophorone or homodsophorones from saturated ltetones containing between 3 and 5 can bon atoms.

A further object is to provide a process wherein a saturated ketone containing from 3 to 5 caroon atoms is effectively cyclized to isophorone or homo-isophcrones While the non-cycllc isomers oi the same number ai carbon atoms or higher condensation products than the primary unsaturated alicarbocyclic ketone product are formed in only small amounts.

An additional object is .to provide amethod of manufacture of isophorone and certain h'omoisonhoroncs which permits' the catalyst to be maintained at substantially initial activity without deterioration over very long periods of time.

l1l'he primary object of the invention is to provide a process for the manufacture of isophorone whichis highly eiiicient and economical.

ilhe preparation oi isophorone by condensation of acetone is well known and a number of cataisophorone by the use of sodamide. Calcium carbide has been suggested as a liquid phase catalyst, but giveslargely very high condensation products. U. S. Patent No. 2,183,127 shows a vapor phase method. of condensing acetone in which isophorone is obtained by contacting ace--V tone vapors with calcium o'iiide,` hydroxide or carbide. l

The preparation of homo-isophor'ones from certain homologues oi acetone has also been described. Ekeley and Howe (J. A.. C.'S. 45, 1922),

show. the condensation of methyl ethyl ketone' German yatent No. 134,982 discloses to homo-isophorones by long-standing at room l temperaturein the presence oi sodium ethylate, while diethyl ketone was condensed 4sirnilarly by Ekeley and Carpenter (J. A. C.' S. 46, 448) at a low temperature to give the corresponding homo- 'isophorones U. S. Patent No. 2,148,103 describes condensation oi methyl propyl and higher ketones in the presence of solid alkali metal oxides, hy-

droxides, amides or alcoholates, the water of reaction being distilled from the reaction mixture and catalyst as fast as formed.

The treatment of several lower iretones is described by Franke and Khler (Ann. 433,v 314)- wherein the ketones were permitted to stand at room temperature in 'the presence of aqueous aliralies or alcoholic allialles. In copendine applications, Serial No. 257,200, filed February 18, 1939, and Serial No. 318,506, filed February 12, 1940, in which one of us is a co-inventor, there is described and claimed a method oi condensing ketones in the presence of concentrated aqueous solutions o alkali metal hydroxides and removing the water oi' reaction as formed' by distillation.

While these prior art methods are eliective in yielding the desired unsaturated alicarbocyclic 1retone, they each have certain inherent disadvantages which preclude their suitability for large technical scale manufacture of lsophorone or homo-isophorones. These will be apparent from consideration of the problems encountered in condensation of acetone to isophorone; the problems being similar with higher ketone condensation.

The treatment of acetone with a condensation catalyst causes a number of condensation reactions to occur-i. e., the treatment does not resultV in a single and unique reaction of condensation. For formation of isophorone to be realized, severe conditions oi treatment have been employed by the use oi' strong anhydrous alkaline substances or concentrated solutions of certain of them. While the formation of isophorone is realized with such catalysts, the use of these strong condensing agents causes the formation of high condensation products like high-boiling condensates, resinous Asubstances and even terry materials, in some instances. When the principal product desired is isophorone, the formation o! thehigh condensate lay-products is responsible i'or a maior loss of yield of the isophorone in the processes. y

In the vapor phase method oi.' condensing acetone,y the catalyst soon becomes coated'with a deposit of carbonaceous materials which reduce, or eventually destroy, its activity. The catalyst coated with a deposit or this nature must either be discarded or subjected to a reactivation treat- 'formation of lsophorone from acetone.

ment for removal oi the deposit and restoration of the activity, either alternative o! which is detrimental to the emciency of th'e process.

Water is one of the products of reaction in the The formation of each molecule of isophorone liberates two molecules of water. Inthe older methods of preparing isophorone outlined above in A which acetone was treated with an anhydrous catalyst, the formed or liberated water of reaction caused the catalyst to soon become ineective or destroyed it and when a concentrated solution was employed, the formed water soon diluted the catalyst solution to an inoperative state under the conditions utilized. Thus in the liquid phase condensation in the presence of sodamide, sodium alcoholate or calcium carbide, the formed water reacts with the catalyst to destroy it. The continual dilution of the concentrated solutions of alkalies, when such were used as catalyst, results in a continually changing reaction medium with respect to the alkalinity thereof, even though all other conditions or variables are maintained constant and, under these conditions, the catalyst solution becomes in time too weak to cause the desired cyclic condensation reaction to isophorone to occur. Later improvements in the art provided distillation as a means of removing the water of reaction as fast as formed. However, the use of concentrated solutions of condensing agents coupled with distillation to remove the formed water is hampered by the formation of high-boiling by-products which represent irretrievable loss of yield to a useful material) owing to. the high alkalinity of the catalyst solution. These high-boiling byproducts are of little value and no known method is available for conversion of them to useful products, so that it was of utmost importance to find a method of keeping their formation low.

We have now discovered that acetone is condensed to isophorone in the presence of a dilute aqueoussolution of an alkali metal hydroxide when liquid acetone is brought into intimate contact with the catalyst solution at a temperature above about 130 C. and that the use of the dilute catalyst solution enables those ,high-boiling byproducts to be maintained at a low value. A temperature above about 130 C. is considerably above the normal boiling temperature of acetone and the acetone is maintained in a liquid state by the use of sumcient pressure to prevent boiling of the reaction mixture. With other variables constant, we have found that the condensation using a dilute aqueous solution of an alkali metal hydroxide gives a low formation of higher condensation products as compared to the amount of these substances formed when a concentrated aqueous solution is employed, with the result that the yield of the isophorone /or homo-isophorone is considerably improved by the process of the present invention.

We have' nowfurther discovered that the water formed by reaction is removable from the reaction mixture by, in effect, extracting it with the product mixture, and this feature enables operation to be conducted in a continuousI manner which is highly emcient. Two phases exist in the reaction mixture, an aqueous catalyst phase and an organic phase. In operation of the process, all of the acetone fed into the reaction zone does not condense to isophorone or other lower or higherv condensation products. Water has no appreciable solubility inthe majority of the condensation products. but it is completely miscible with and soluble in acetone. Since the organic phase contains a preponderance of acetone therein, wateris appreciably soluble in this phase and by continuously withdrawing a part of the phase from the reaction zone, the water of reaction is removed therefrom. The operation f the property of appreciably dissolving water and they are thus operative in the process.

In substance, the process of our invention comprises continuously introducing and commingling a. saturated ketone containing between 3 and 5 carbon atoms in the liquid state with a dilute aqueous solution of an alkali meal hydroxide, the reaction zone being maintained at a temperature preferably between 150 C. and 200 C. and under at least suiiicient pressure to prevent boiling therein, and continuously withdrawing a portion of the organic phase from the reaction zone, the concentration of hydroxide in dilute aqueous solution being maintained substantially constant by the water of reaction being carried out of the reaction zone with the efiiuent organic phase and, if more water than that formed in the reaction is extracted, by feeding the ,needed water into the reaction zone along with the input ketone.

In order that the condensation reaction of a ketone to form the unsaturated alicarbocyclic ketone (isophorone or homo-lsophorone) be possible, it is necessary that at least one hydrogen atom be linked directly to each alpha carbon atom of the ketone. The ketones employed as reactants in the process of the invention are acetone, methyl ethyl ketone, methyl propyl ketone, diethyl ketone and methyl isopropyl ketone and each of these open-chain saturated ketones possesses the required structure in having at least' Aone hydrogen atom (some have two and some -have three) linked directly to each alpha carbon atom.- Acetone is a preferred reactant in that it is most reactive of the ketones, the others requiring, in general, higher reaction temperatures and longer times of residence in the reaction zone for best results.

The temperature maintained in the reaction zone is from about C. to the critical temperature of the ketone reactant. Since the desired reaction is effected in the liquid phase, the upper limit is determined by the critical temperature of the ketone employed as reactant. In the case of acetone, the critical temperature is about 235 C.; with methyl ethyl ketone, it is about 261 C.; and with methyl propyl ketone it is about 282 C. The process is preferably executed at a temperature between C. and 200 C., excellent results being obtained with acetone in the neighborhood of C.

The pressure required to be maintained will vary with the particular operating temperature and the particular ketone reactant employed in the process. As is well-known. the pressure needed will be higher for higher operating temperatures, and since the materials in the reaction zone are kept entirely in the liquid phase in the process, although the operating temperature is above the normal boiling temperature of some constituents therein, the pressure employed is considerably above atmospheric pressure, and at least equal to the sum of the partial pressures assumo of each of the components present in the reaction zone. Ordinarily a pressure ot say 15 lbs. per square inch above the required minimum is maintained so as to satisfactorily prevent any boiling in the reaction zone which might occur, owing to even' minor iiuctuations of temperature in the executionof the process.

The catalyst is a dilute aqueous solution of an alkali metal hydroxide. By a dilute aqueous solution is meant one containing between 15 per cent and 35 per cent by weight of the alkali metal hydroxide with respect to the aqueous solution. Expressed diderently, the dilute aqueous solution contains a weight ratio of water to alkali metal hydroxide between 5.66:l and 136:1. 1n the operation oi the process the concentration of hydroxide in aqueous solution is maintained substantially constant at a value within the indicated range. With other variables constant, the ability ci the organic phase to extract water, including the Awater formed by the reaction, is primarily a function of the amount of ketone reactant present in the organic phase, and this is determined by the time of residence of the ketone in the reaction zone. In general, the longer the time of residence in the reaction zone, the lesser will be the amount of unreacted ketone in the organic phase, a portion of which is withdrawn continuously in an amountequal tothe material fed to the reactor. (The time of residence is' in timeunits and equal to the volume ci organic phase present in the reactor divided by the volume of ketone per unit time fed tothe reactor.) With the use of shorter. residence times, larger amounts of water are extracted with the eluent organic'phase and, in some cases, the aqueous catalyst phase would tend to become concentrated. This dlilculty is avoided by continuously feeding water in with the ketone fed to the reactor. The amount of water fed into the lreaction. zone is determined by the residence time, the temperature of reaction, the concentration oi.' hydroxide used in the aqueous phase and the particular ketone employed. The use of.' acetone as the reactant requires more water to he introduced than with the higher ketones and in some cases, especially with the higher ketones, no water need be added.

any alkali metal hydroxide is ,suitable for use in the aqueous catalyst phase. Ordinarily, because oi cheapness and ready availability, sodium hydroxide is a preferred catalyst although lithium, rubidiurn, or cesium hydroxides are employed, if desired. The most preferred catalyst is potassium hydroxide which, although somewhat more expensive than sodium hydroxide, has greater activity than the hydroxide of sodium. Since substantially no catalyst is consumed in the process in contradistinction to prior art methods requiring comparatively large requirements of catalyst, our method has practically no cost for catalyst other than the original price. The life of the catalyst solution appears to be indefinite and the only loss is a few hundredths of a per cent carried out with the efiluent organic phase.

In the process, the organic phase is intimately contacted or coxnmingledy with the aqueous catalyst phase. Any means for churning and mixing the two phases is satisfactory. A suitable reactor is a turbo mixer which is a closed vessel iitted with revolving paddles. Another suitable means of obtaining the required agitation and turbulence is to pump, at preferably high velocity. the mixture of two phases through a time tank iitte'd with bailes, perforated plates or the like, the exit of the tank `connecting to the intake of the pump.

AThe volumer'atio of the two phases in the reaction zone'has little effect as a variable in the results'obtained, provided it is kept within reasonable limits of say 5 to 1 either way. Excellent performance of the process is obtained with equal volumes of organic phase to aqueous phase in the reactor or reaction zone, ferred ratio. A

'ihe process of the invention is illustrated in the accompanying drawing by Figure 1 which gives a simple arrangement of suitable apparatus for executing the process. Figure 2 shows a combination of more preferred equipment for operation of the process.

In Figure 1, the liquid ketone reactant is pumped into the system by ketone i'eed pump I through pipe 2 to input control valve 3, entering the reactor which is' a turbo mixer having an internally rotating paddle wheel .and fitted with heating means such as an internal steam coil (not shown) through pipes Ili and l. If needed, water is pumped into the system by means of water feed pump 1, passing through pipe 8 to control valve 9 and into the 'reactor by means of pipes IU and i. Before Starting operation of the system, reactor 6 is iilled with the desired quantity oi' the dilute aqueous solution of an alkali metal hydroxide. One-half of the volume of the reactor is filled with thedilute aqueous catalyst solution when the preferred ratio of one volume of organic phase to one volume of aqueous phase is used. The reaction mixture of catalyst solution. unconverted ketone and products is withdrawn upwards from the reactor 8 through conduit It to combined cooler and separator I3 wherein the material is partially cooled and stratification ci" the organic phase and aqueous phase occurs. The upper layer` in cooler and separator I3 is the organic phase; the lower layer being the' aqueous phase which returns to turbo mixer by means oi pipe I2. Liquid organic present in the eilluent organic phase fed to the' recovery system. In the case of condensation. v 4of acetone. the major "constituent 4will be unreacted acetone along with which will be mesityl oxide, diacetone alcohol, the desired isophorone, phorone and higher condensation products. When ketones containing 4 carbon atoms' or'5 vcarbon atomsare employed as reactants, the constituents will be similar homologues and owing to the more complex structure of the 4 and 5 carbon atom ketones, isomers of particular constituents will be present. For example, in the conden-saf tion of lmethyl ethyl ketone. according to the Il which water is removed from the reaction zone -stereo and optical isomers.

process of the invention. four structural isomers of the homo-isophorone are possible. excluding The for-mation of products like mesityl oxide,A phorone, and higher unsaturated condensation products forni water as a product of reaction, as does isophorone,

this being the pre- 4` masacre in the invented process by the `eiliuent organic phase.

The recovery of the .eiiluent organic phase with isolation of the lisophorone or homc-isophorones is handled in several ways. Mesityl oxide and dlacetone alcohol are in themselves commercially valuable'products and by subjecting the eiiluent mixture to fractional distillation, these along with the unconverted` acetone and other constituents can be separated. Fractional distillation in a continuous manner requires a plurality of columns and when lower condensation products like mesityl oxide and diacetone alcohol are not desired to be isolated as products, the crude organic mixture may be subjected to the selective reversion process described and claimed in copending application of McAllister and Bailey, Serial No.1404,512, filed July 29, 1941. That process enables the crude organic mixture to be treated so that products like mesityl oxide and diacetone alcohol are selectively reverted back to parent acetone without changing isophorone present in the'mixture. The recoveredacetone obtained by any method can be returned as feed to the condensation process. Those higher condensation products which are not revertible to the parent ketone -by al now known method or are not of particular value in themselves are obtained in minimum amount by the process of the invention,

and since` the lower products can be reverted to 30 the parent ketone as indicated, the only loss of yield of the unsaturated alicarbocyclic ketone, isophorone or homo-isophorones, is in these higher products.

A, more elaborate arrangement of apparatus v and ilow of the process is shown in Figure 2. Ketone reactant, by means of pump 2l, pipe 22 and control valve 2l, is fed to feed tank 24 which is an intermediate storage vessel for feed Y' to the reaction system. Water, if needed, is supplied to tank 26 through pump 25, pipe 2l and control valve 2T. The feed is withdrawn from tank 24 through line 28 to pump i@ which pumps the feed into the reaction and supplies the necessary pressure needed to keep the materials in 45 the reaction system in the liquid state and prevent boiling therein. From pump Il, the feed is passed through pipe 8| to feed control valve 32 and, by means of pipe 33, to heater 34 which supplies the heat needed to maintain the re-- action zone at the desired temperature. The feed passes from heater 34 by pipe 35 which is tapped into pipe 40. The reaction zene is a circulating system consisting of pipe le, circulation pump 4| of large capacity, pipe l2 and time tapped -into' pipe l2 and the material is fed to separator Il where stratification of the organic 55 phase and the aqueous phase occurs. The adueousphase is returned from separator l! by means of pipe 4E to pipe 40 in the suction side of pump 4I in the circulating system. Valve 4l connected in' pipe 46 is used to control the levell of the phases in separator 4I. The eiiiuent orsanic phase passesvfrom separator 45 through pipe Il to cooler 4l where the phase is cooled and from which the material passes through linell to a conventional pressure regulatingyalve l2 which controls the pressure on the system and is actuated through connection B3 tapped into pipe l of the circulating system. The efiiuent organic layer is taken 'from valve 52 and runto the recovery systeminot shown). 'The recovery and separation of the products is done in the same manner as described in the. system of flow shown in Figure l.

vWhen elfectin'g the condensation of ketones containing four or iive carbons under certain conditions (long residence time, towards the upper limit of the hydroxide concentration, etc.) it is sometimes found that the aqueous catalyst solution tends to become diluted from the particular and desired caustic concentration by the inability of the eiliuent organic phase to extract sumcient water from the reaction zone. .This excess water is removable from the system by several ex pedients. Thusyin the system shown in Figure 2, aunit is inserted inline Il through which catalyst solution is returned from separator I5 back to the reaction zone, in which unit, removal of water with concentration of the aqueous hydroxide i phase is effected. For this purpose, the unit is a continuous evaporator wherein the caustic solution is concentrated and the concentrated solution then returned continuously into the reaction zone. If desired, a continuous liquid phase extraction unit can be used in which' a liquid extractant like a butyl alcohol which will remove water and concentrate the caustici solution is suitable. Another methcd which is effective in obtaining the desired result with the process is to increase the ability of the organic'phase to extract water from the aquebus phase in the system by continuously feeding in a lower alcohol such as methyl alcohol, ethyl alcohol, normal propyl alcohol or isopropyl alcohol into the reaction zone. Such a substance is inert in the reaction zone, but greatly assists the organic phase to extract water from the aqueous phase' so that the concentration of hydroxide in the aqueous solution will remain constant and not become diluted by failure of the organic phase to extract or remove ."sufiicient water from the reaction zone.

In starting up the process in either arrangement of apparatus shown in Figure 1 or Figure 2. the aqueous catalyst solution is introduced into the 'reaction zone and the air therein is displaced by pumping in the ketone reactant. No withdrawal of the organic phase from the reaction zone is permitted until the desired amount of reaction has occurredafter which withdrawal is started and fresh feed introduced. During the starting up period, pressure is maintained on the system by means of the pumps so that the matet mls ual-einem in the uqiud state. After atming, the process soon settles down to a steady state. y ,t

The saturated ketone employed as reactant and *Y condensed to the mono-unsaturated alicarbocyclic ketone is ordinarily the sole reactant fed to the system in the process of the invention. Mixed isomeric products are obtained by using a plurality of the individual saturated ketones containing 3 to 5 carbonzatoms. l

Fbr the purpose of further :illustrating the process of lthe invention, the following examples are given, but it is to be vunderstood that the invention is not to be' construed as limited to any details given therein.

Example I l.acetone was condensed continuously in the 5 presence of a dilute aqueous solution of sodium accanto hydroxide, the hydroxide concentration in aqueous solution being maintained at about 25 per cient throughout the run. The lacetone was processed in apparatus similar to that shown in Figure 1. Acetone was continuously introduced at a rate of about 840 ce. per hour along with 6o cc. per hour of water which maintained the caustic concentration constant. Equal volumes of organic layer to catalyst layer were used in the reaction Vzone andthe temperature therein was maintained at 170 C. The size of the mixer was such that the residence time of the acetone therein was about 37 minutes. The eiiiuent organic phase was iiowed from the reaction system' toa fractionating column in which the unreacted acetone was strippedfrom the mixture. The residue was permitted to accumulate and was later distilled to separate the constituents thereof.

The composition of the organic layer from the reactor during the run was as tabulated below:`

Weight i Constituent pement 'Acetone.

Mestyl nxidn Diacetone alcohol Isophorone A Heavy end-i Water of "omle- Water of injection ewa-erw? Oi the acetone converted. the distribution of the constituents in lWeight percentage of the acetone converted was as given in the following table: Y

Constituent Weight percentage Total products Mesityl n'ririn Diacetono alcohol Isophorone. Heavy ends.

In this run, a 78 per cent yield of isophorone .was obtained in the product containing 9' or more carbon atoms..

Example Il 'C'omposittonof product-weit per cent.'

Acetone 79 70.9 79.0 76.7 Mesityl oxide 1 2.7 3.3. 4.1 Diacetone Y l alcohol-- 1.5 5.5 2.o 4.0 Isophoy rohe 3 4.8(5) 2.1(4) 5.5(ul Heavy ends- I 0.5 1.6(8) 0.4(2) 1.9(3) Water of condensa,- tion 1 2.3 1.3 2.9 Water in- Jected 14 12.1 11.3 4.9

Weight per cent acetone converted to;l

Total products 19 19.4 lidi 19.3 Mesityl oxide -..1---- 4 3.6 to di. Diacetone alcohol 4- 7 6.3 Siti Isophorone 6 7.0 i231 Heavy ends 2 2.5 6.o?. Isophoronc yield:

Weight per cent isophorone in Cn and higher 79 74.3 83.7 Weight per cent KOH in product 0.041 0.062

Example III Acetone .was condensed in the presence of dilute aqueous potassium hydroxide in an apparatus similar to that shown in Figure 2. The run was continued for 178 hours and the catalyst was in no way deteriorated at the end of this time. The

`aqueous catalyst solution was maintained with 30.3 per cent potassium `hydroxide therein. The temperature of operation in the reactor was 169" C. under a pressure of 290 lbs, per sq. in. and the phase ratio of organic phase to aqueous phase was 12:1. The conditions andv results of the run are tabulated below:

Conditions in reactor:

Acetone fed to reactor, g. p. h. 175.9 Water fed to reactong. p. h. 18.3 Residence time,y min. 17.5 Wt. per cent water in emuent organic layer 14.1 Wt. per cent KGH in eiliuent organic layer 0.024

Mol per cent acetone converted to:

Mesityl oxide 5.9 Isophorone 6.3 Heavy ends 1.6

' Percentage yields in isophorone and heavy' ends: Isophorone 79.8 Heavy ends 20.2

used and the pressure maintained on the reactor 'was about 300 lbs. per sq. in.

vso 3120 10x40 Vs1 4o Weightper cent water ln feed application is' a continuationin-part of our co-pending application, Serial No. 396,192, y A illed Mayl, 1941.

witnrespect to the hydroxide and water therein at a temperature oi' from 130 C. to the critical temperature of said ketone while maintaining sumclent pressure in said reaction zone to keep the entire contents therein' in the liquid state,

' continuously withdrawing from said reaction zone a portion of liquid organic phase containing water extractedfrom said dilute aqueous solution by the contacting therewith, and continuously in- -solution substantially constant.

2. A process for. producing isophorone' which comprises continuously introducing acetone into a. reaction zone and intimately contacting said ketone with a dilute aqueous solution containing between 15 and 35 per cent by weight of an alkali metal hydroxide with respect to the hydroxide and water therein at a temperature of from 130 C. to the critical temperature of acetone of about 235 C. while maintaining sufficient pressure in said reaction zone to keep the entire contents therein inthe liquid state, continuously withdrawing from said reaction zone a portion of liquid organic phase containing water extracted from said dilute aqueous solution by the contacting therewith, and continuously introducing into said reaction zone suiiicient water with respect to the water removed therefrom in said eiiiuent organic-phase to maintain the concentration of the hydroxide in said dilute aqueous solution substantially constant.

3. A process for producing an isophorone whichy comprises continuously introducing and commingling a 3 to 5 carbon atom saturated ketone with a dilute aqueous solution of an alkali metal hydroxide at a temperature between 150 C. and 200 C. while maintaining the reaction mixture in the liquid state by application of sulcient the comminsling therewith, and continuously introducing into the reaction mixture sufiicient water with respect to water withdrawn therefrom in said eiiiuent organic phase so as to maintain the concentration of said hydroxide in said dilute aqueous solution substantially constant at a value between and 35 per cent by weight.

6. A process for producing isophorone which comprises continuously introducing and ccmmingling acetone with a dilute aqueous solution of potassium hydroxide at a temperature between 150 C. and 200 C. while maintaining the reaction mixture in the liquid state by application of sufficient pressure to prevent boiling thereof, continuously withdrawing from the reaction mixture a portion of liquid organic .phase containing water extracted from said dilute aqueous solution by the commingling therewith, and continuously introducing into the reaction mixture sufficient water with respect to water withdrawn therefrom in said eiiluent organic phase so as to maintain the concentration of said hydroxide in said dilute aqueous solution substantially constant l at a value between 15 and 35 per cent by weight.

7. A process for producing an isophorone which comprises continuously introducing into a reaction zone and intimately contacting therein a saturated ketone of 3 to 5 carbon atoms with a dilute aqueous solution of an alkali metal hydroxide at a temperature of from 130 C. to the critical temperature of said ketone; continuously transferring a portion of the reaction mixture from said reaction zone to a stratiiicationaonc wherein said transferred reaction mixture separates into an aqueous phase and an organic phase.

. suiilcient pressure being maintained in said repressure to prevent boiling thereof, continuously withdrawing from the reaction mixture a portion of liquid organic phase containing water extracted from said dilute aqueous solution by the commingling therewith, and continuously introducing into the reaction mixture suiicient water with respect to water withdrawn .therefrom in said eiuent organic phase so as to maintain the concentration of said hydroxide in said dilute aqueous solution substantially constant at a value between 15 and 35 per cent by weight.

4. A process for producing isophorone winch comprises continuously introducing and commingling acetone with a, dilute aqueous solution of an alkali metal hydroxide at a temperature between 1509 C. and 200 C. While maintaining the reaction mixture in the liquid state byl application of suflicient pressure to prevent boiling thereof, continuously withdrawing from the reaction mixture a portion of liquid organic phase containing water extracted from said dilute aqueous solution by the commingling therewith, and continuously introducing into the reaction mixture sufficient water with respect to water withdrawn therefrom in said yeilluent organic phase so as to maintain the concentration of said hydroxide in said dilute aqueous solution substantially constant at a value between 15 and 35 per cent by weight.

5. A process for producing isophorone which comprises continuously introducing and commingling acetone with a dilute aqueous solution of sodium hydroxide at a temperature between 150 C. and 200 C. While maintaining the reaction mixture in the liquid state by application of suiiicient pressure to prevent boiling thereof, continuously withdrawing from the reaction mixture a portion of liquid organic phase containing water4 extracted from said dilute aqueous solution by action zone and in said stratification zone to keep the entire contents therein in the liquid state; continuously returning stratified aqueous phase from said stratification zone to said reaction zone: continuously withdrawing from said stratification zone stratied liquid organic phase containing water extracted from said dilute aqueous solution by the contacting therewith; and continuously introducing into said reaction zone suicient water with respect to the water withdrawn in said efnuent organic phase to maintain the weight ratio of water to said alkali metal hydroxide in said dilute aqueous solution substantially constant at a value between 5.66:1 to 1.86z1.

8. A process for producing isophorone which comprises continuously introducing into a reaction zone and intimately contacting therein acetone with a dilute aqueous solution of an alkali metal hydroxide at a temperature of from 130 C. tothecritical temperature of acetone of about 235 C.; continuously transferring a portion of the reaction mixture from said reaction zone to a stratication zone wherein said transferred reaction mixture separates into an aqueous phase and an organic phase, sufficient pressure being maintained in said reaction zone and in said stratification zone tc keep the entire contents therein in theliquid state; continuously returning stratified aqueous v phase from said stratiiication zone to said reaction zone; continuously withdrawing from said stratification zone stratiiied liquid organic phase containing water extracted from said dilute ,9. A process ior producing isophorone whichv inirodueiu comprises continuously into a ne action zone and intimately contactinl therein acetone with a dilute aqueous solution ot sodium lhydroxide at a temperature oi .from 130. C. to the critical temperature 'foi acetone o! about- 235 C.; continuously .transierrinz aportionot tho `reaction mixture. from said Areaction :ma to -a stratification sone wherein said reaction mixture separates into an aqueous puse and an organic phase, simcient pressure beine maintained in said reactlon'sone-and in said stratication zone to keep the entire contexto therein in the liquid state; continuously returning stratiiied aqueous phase from said stratification zoneI to said reaction sone; continuously withdrawing from said stratiiication zone stratitied liquid organic phase containing waterv extracted from said dilute aqueous solution by the contacting therewith; and continuously introducing into said reaction sone auicient water with respect to the water withdrawn in said eilluent organic phase to maintain the weicht ratio of water to said sodium hydroxide in said' dilute aqueous solution substantially constantat a vvalue between 5.68z1'to 136:1. l

10. A process for producing isophorone which tionloneandintimatelycontactingthereinacetone witnadilute aqueous solution oi' .potassium .'hydroaide atatemperatureoiirom 130 @tothe critical temperature of acetone ot about 235 C.;

sonetokeeptheentirecontentstherein in the liquid state; continuously returning stratiiied aqueous phase from said stratification sone to said'reaction lone: continuously withdrawing i from said stratification sono stratiiied liquid or- BEAVER A. BALLARD. VERNON E. HAURY.

. v'7` commisescontinuouslyintroducingintoarcac-` 

